1. Field of the Invention
This invention relates to an annular seal, and especially to a preloaded circumferential sliding seal for use on a piston in a rocket propellant tank.
2. Description of the Prior Art
One of the main sources of fuel for the energization of rocket engines is liquid propellant fuel. The liquid propellant is stored in a tank, often cylindrical in shape, within the rocket engine. To avoid the problems which occur when positive expulsion of the liquid fuel is not achieved, pistons are often provided within the tanks to maintain a constant pressure against the liquid propellant and force the propellant into the tank outlet during operation of the engine.
However, to prevent leakage of the liquid propellant past the piston into the rear section of the tank, which may house a gas generator of the solid propellant type, for example, whose materials may be incompatible with the liquid propellant, it is necessary to seal the areas where the piston meets the body of the tank or the central shaft which is often used in the tank to stabilize the orientation of the piston.
It is also important to provide a seal which will provide for long-term sealing of the propellant, since the rocket may be stored for many years before being used.